Introdução

A Judy array is a complex but very fast associative array data structure for
storing and looking up values using integer or string keys. Unlike normal
arrays, Judy arrays may be sparse; that is, they may have large ranges of
unassigned indices.

A Judy array consumes memory only when populated yet can grow to take advantage
of all available memory. Judy's key benefits are: scalability, performance,
memory efficiency, and ease of use. Judy arrays are designed to grow without
tuning into the peta-element range, scaling near O(log-base-256) -- 1 more RAM
access at 256 X population.